Method Article

Ultra-Low Hydrogen Peroxide Detection via Synergistic Nernst Potential Effect in Organic Electrochemical Transistors

245 views

⸱

DOI:

10.3791/70467

⸱

March 31st, 2026

 ,  ,  ,  ,  , 
1College of Integrated Circuits, Taiyuan University of Technology

Corresponding Authors: Xiaojie Chai <chaixiaojie@tyut.edu.cn>, Jianlong Ji <jijianlong@tyut.edu.cn>

In This Article

Summary

Here, we present a protocol for ultra-low detection of hydrogen peroxide based on the synergistic Nernst effect. This protocol covers the fabrication of stacked-layer poly(3,4-ethylenedioxythiophene): bromothymol blue (PEDOT: BTB)/polystyrene sulfonate (PEDOT: PSS), and platinum microelectrode (Pt), as well as the determination of the optimal operating point for the as-constructed H2O2 sensor.

Abstract

The organic electrochemical transistor (OECT)-based synergistic Nernst potential—generated via the Pt gate electrode catalyzing hydrogen peroxide (H2O2) and the interaction between bromothymol blue (BTB) molecules and hydrogen ions (the by-product of H2O2 catalysis)—is leveraged for the ultra-low detection of H2O2 down to 1.8 × 10-12 M, with a broad linear detection range from 10-11 M to 10-3 M. The formation of this potential is determined by selecting a source-drain voltage (VDS) and a gate voltage (VG) of −0.6 V as the optimal operating points, and by adopting the stacked-layer poly(3,4-ethylenedioxythiophene):bromothymol blue/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:BTB/PEDOT:PSS) as the semiconducting channel material. In addition, relevant verification is provided by characterizing the carrier (de)doping capability of the stacked layers using UV–vis spectroscopy, identifying the optimal operating point via electrochemical measurements, and evaluating the sensing performance of the as-constructed OECT-based H2O2 sensor using single-stage constant-voltage scanning. Finally, the OECT-based H2O2 sensor is fabricated via a micro-nano manufacturing process, including the preparation of stacked semiconducting layers by spin-coating and the fabrication of microelectrodes via the lift-off process and magnetron sputtering. This methodology can open a broad avenue for the ultra-low detection of analytes through enzyme-catalyzed reactions.

Introduction

Hydrogen peroxide (H2O2) is a ubiquitous by-product of numerous enzyme-catalyzed biochemical reactions, including those mediated by lactate oxidase, glutamate oxidase, and glucose oxidase1. Its pervasive presence in a wide range of physiological and pathological processes2,3,4 makes it a critical biomolecule for understanding human health and disease states. Therefore, accurate detection of H2O2 at ultra-low concentrations is essential for gaining precise insights into bodily conditions, driving significant interest among researchers in developing sensitive detection methodologies with a low limit of detection (LOD).

Traditional H2O2 detection methods5,6, such as spectroscopy, chromatography, and chemiluminescence, have laid the foundation for quantitative analysis but suffer from inherent limitations that hinder their widespread applicability. These techniques typically rely on bulky, expensive instrumentation and require specialized professional expertise, making them impractical for on-site, portable, or point-of-care detection scenarios. Thus, there is an urgent need for alternative detection technologies that combine high sensitivity with miniaturization, low cost, and ease of use.

With the advancement of micro-nano technologies, organic electrochemical transistors (OECTs) have emerged as a promising platform for biosensing applications, owing to their inherent advantages, including miniaturization, low operating voltage, excellent signal amplification capability, and biocompatibility7,8,9. OECT-based sensors have been increasingly explored for H2O2 detection, with a primary focus on modifying H2O2-sensitive materials onto microelectrodes to enhance detection sensitivity. For example, Cicoira et al.10 constructed an OECT-based H2O2 sensor with a linear detection range from 5 μM to 103 μM and a low LOD of 5 μM when Pt was used as the source, drain, and gate materials. Guo et al.11 fabricated an OECT on a flexible poly (ethylene terephthalate)(PET) substrate and a transwell support. The device employed a screen-printed carbon paste electrode modified with carbon nanotubes and Pt nanoparticles as the gate electrode, and PEDOT: PSS as the channel material, exhibiting a linear detection range of 0.5-100 μM and an LOD of 0.2 μM for H2O2. Qi et al.12 reported a donor-acceptor (D-A) type ambipolar single organic mixed ionic-electronic conductor (OMIEC) polymer-based OECT, which exhibited a linear detection range of 0.001-100 μM and an LOD of 1 nM for H2O2. The aforementioned H2O2 sensor achieved low LOD mainly dependent on the Nernst potential generated by the Pt-based gate electrode catalyzing H2O2, which could regulate the electrochemical (de) doping state of the channel layer for utilizing the excellent signal amplification capability. Thus, prior studies in this field have established a solid theoretical and experimental basis for further optimization.

The core goal of this study is to develop a highly controllable and sensitive OECT-based H2O2 sensor by further harnessing the Nernst potential, a key mechanism underlying the performance of electrochemical sensors. To achieve this, we propose a synergistic Nernst potential mechanism13, which relies on a cascade reaction involving two key components: Pt-based gate electrodes that electrocatalyze H2O2, and a stacked semiconductor channel layer (PEDOT: BTB/PEDOT: PSS) that interacts with hydrogen ions generated as a by-product of H2O2 catalysis. This design is grounded in established research: bromothymol blue (BTB), a well-known chemical indicator for weak acids and bases14, has been successfully integrated with PEDOT (as PEDOT: BTB) on the OECT gate or channel layer for pH sensing in prior studies, validating the feasibility of the cascade reaction central to our approach.

Compared to alternative OECT-based H₂O₂ detection methods, our synergistic Nernst Potential strategy offers distinct advantages. Unlike conventional designs that rely solely on the catalytic activity of Pt-based gate electrodes to generate Nernst potential, our approach enhances controllability by coupling this catalytic process with the pH-responsive behavior of the stacked channel layer. This synergy not only improves the sensor's sensitivity but also enhances its stability and tunability, addressing key limitations of existing OECT-based sensors. Furthermore, this technique aligns with the broader trend in OECT-based biosensing, which emphasizes the integration of functional materials and innovative reaction mechanisms to push the boundaries of detection performance.

In the context of broader electrochemical detection literature15,16,17,18,19,20,21, OECTs have become a cornerstone of portable biosensing due to their ability to amplify weak electrochemical signals, making them ideal for low-concentration analyte detection. Our work builds on this foundation by refining the Nernst potential-driven mechanism, offering a new perspective on how to optimize OECT performance for H2O2 detection. For readers considering the applicability of this method, our design is particularly well-suited for scenarios requiring high sensitivity, portability, and controllability, such as point-of-care diagnostics, in vitro monitoring, and on-site environmental or biological sample analysis, where traditional methods are impractical. By clarifying the conceptual framework and advantages of our approach, this introduction provides readers with the necessary context to evaluate whether this method aligns with their specific application needs.

Protocol

1. Fabrication and characterization of stacked PEDOT: BTB/PEDOT: PSS semiconductor film

  1. Sample preparation
    NOTE: When preparing the single-layer PEDOT: PSS, do Step 1.1.1. When preparing the stacked-layer PEDOT: BTB/PEDOT: PSS, perform Step 1.1.2.
    1. Prepare the single-layer PEDOT: PSS via spin-coating.
      1. Filter the commercial PEDOT: PSS solution using a 0.45 μm filter (polyethersulfone PES).
      2. Take 884 μL of filtered PEDOT: PSS, 1 μL of 0.1 wt% dodecylbenzene sulfonic acid (DBSA), 50 μL of 5 wt% ethylene glycol (EG), and 5 μL of 0.5 wt% 3-glycidoxypropyltrimethoxysilane (GOPS) and mix them thoroughly to form a mixed solution (i.e., PEDOT: PSS precursor).
      3. Stir the PEDOT: PSS precursor overnight using a magnetic stirrer, then sonicate for 5 min
      4. Spin-coat the PEDOT: PSS semiconductor film to bridge the source and drain electrodes using a Spin Coater at a spin speed of 4200 rpm, an accelerated speed of 200 rpm s-1, and a maintenance time of 60 s.
      5. Bake the film at 130 ℃ for 15 min in an oven, then pipette 10 μL of concentrated sulfuric acid (H2SO₄) onto the film to remove excess PSS.
      6. Rinse the film subsequently with deionized water, then bake at 130 ℃ for 10 min.
    2. Prepare the stacked-layer PEDOT: BTB/PEDOT: PSS via electrodeposition.
      1. Prepare a solution containing 42 μL of 10 mM 3,4-ethylenedioxythiophene (EDOT), 0.02496 g of BTB, 40 mL of 1 mM phosphate buffer solution (PBS), and 0.4044 g of potassium nitrate (KNO3). Mix and shake for 10 min until a red solution is obtained.
      2. Electrodeposit PEDOT: BTB onto the spin-coated PEDOT: PSS layer using the cyclic voltammetry (CV) method of a dual potentiostatic electrochemical workstation. Short-circuit the source (S) and drain (D) electrodes to use them as the working electrodes, use a saturated calomel electrode as the reference electrode, a Pt wire as the counter electrode, and the mixed aqueous solution as the electrolyte.
      3. Apply an electric potential ranging from 0 to 1 V on the working electrode at a scan rate of 0.1 V⋅s-1 for 15 cycles.
      4. Clean the electrodeposited channel with deionized water, then dry at room temperature.
  2. Scanning electron microscope (SEM), atomic force microscope (AFM), ultraviolet-visible (UV-vis) spectroscopy, and electrochemical characterization.
    1. Perform morphological characterization of the films using SEM and AFM.
      1. Deposit the single-layer and stacked-layer films onto the Au sheet, respectively, using the Spin Coater at a spin speed of 4200 rpm, an accelerated speed of 200 rpm s-1, and a maintenance time of 60 s.
      2. Operate the SEM at acceleration voltages of 1 kV and 3 kV in secondary electron mode to observe the surface and cross-sectional morphologies of the as-prepared stacked-layer film, respectively.
      3. Measure the single-layer film (thickness below 115 nm) using a high magnification of 40,000 ×. Measure the stacked-layer film (total thickness 361 nm) using high magnifications of 10,000 × and 40,000 × to elucidate the electrodeposition of the stacked-layer film onto the Au sheet.
      4. Adopt the tapping mode of an AFM to observe the surface roughness variations of the single-layer and stacked-layer films.
      5. Set the AFM scanning range to 5 μm × 5 μm. Record the 3D morphology and calculate the root mean square roughness.
    2. Characterize the photoelectrochemical properties of the stacked layers using UV-vis spectroscopy. Set the wavelength range from 200 nm to 800 nm, optical resolution to 0.73 nm, slit size to 10 μm, integration time to 11 ms, and temperature control to 20–30 °C.
      1. Spin-coat the stacked-layer film onto the indium tin oxide (ITO) at a spin speed of 4200 rpm for 60 s with an accelerated speed of 200 rpm s-1.
      2. Select pH buffer solutions ranging from pH 3 to pH 9 at intervals of two orders of magnitude as the electrolyte for the spectrophotometer cell, and place the modified ITO electrode in the spectrophotometer cell aligned with the light path.
      3. Use a micro-injection pump to successively add and remove 2 mL of electrolyte solutions with different pH values into the spectrophotometer cell.
      4. Measure and acquire the absorption spectra of the stacked-layer PEDOT: BTB/PEDOT: PSS in each pH solution.
      5. Place a Pt wire in the spectrophotometer cell, and connect the working electrode (WE) of the dual potentiostatic electrochemical workstation to the Pt wire. Apply voltages of +0.6 V and -0.6 V. Connect the control electrode (CE) of the dual potentiostatic electrochemical workstation to the modified ITO electrode.
      6. Prepare H2O2 solutions (10-11–10-3 M) in 0.1× PBS with a conductivity of 34.39 ± 0.73 mS·cm-1. Place the modified ITO electrode in the spectrophotometer cell.
      7. Use a micro-injection pump to successively add and remove 2 mL of electrolyte solutions with different H2O2 concentrations into the spectrophotometer cell.
      8. Measure and acquire the absorption spectra of the stacked-layer PEDOT: BTB/PEDOT: PSS in different H2O2 solutions.
    3. Determine gate operation points using electrochemical measurement.
      1. Conduct CV measurements in 20 mL of H2O2 solutions with different concentrations (configured in 0.1× PBS, ranging from 10-3 M to 10-11 M at intervals of two orders of magnitude) with the same conductivity of 34.39 ± 0.73 mS cm-1.
      2. Use a Pt wire as the working electrode, the single-layer film modified on the Au sheet as the counter electrode, an Ag/AgCl electrode as the reference electrode, and H2O2 solutions of different concentrations as electrolytes, respectively.
      3. Apply an electric potential ranging from -1 to 1 V on the working electrode at a scan rate of 0.1 V⋅s-1.
      4. Measure the electrolyte voltage (VE) in 0.1 × PBS (equivalent to 1 mM PBS) without mixing H2O2.
      5. Introduce another Ag/AgCl electrode into the original OECT system (including source, drain, Ag/AgCl gate electrode, and stacked-layer PEDOT: BTB/ PEDOT: PSS semiconductor film), and electrically short-circuit the additional Ag/AgCl electrode and the source electrode in the original OECT system.
      6. Connect an oscillograph to the additional Ag/AgCl electrode, apply a measurement duration of 2 s and a frequency of 10 kHz, and measure the VE.
      7. Measure the scanning spectra of VE in 0.1 × PBS with different H2O2 concentrations (ranging from 10-11 M to 10-3 M at intervals of two orders of magnitude) with the same conductivity of 34.39 ± 0.73 mS cm-1 under VG of ±0.6 V and the VDS of -0.6 V, respectively.
      8. Acquire the middle value of the scanning spectra and use it as the quasi-equivalent value of VE.

2. Preparation of the H2O2 sensor based on the traditional lift-off microfabrication process

  1. Grow a 500 nm-thick SiO2 insulating layer on a three-dimensional (3D) Si substrate, (i.e., 3D silicon oxide layer), then perform ultrasonic treatment with acetone, alcohol, and deionized water for 5 min each in sequence. Dry under nitrogen for 1 min.
  2. Spin-coat a layer of negative photoresist ROL-7133 on the silicon oxide layer using a Spin Coater (Step 1: rotation speed 500 rpm, time 25 s, acceleration 100 rpm/s; Step 2: rotation speed 3,000 rpm, time 54 s, acceleration 200 rpm/s; Step 3: rotation speed 4,000 rpm, time 6 s, acceleration 1,000 rpm/s).
  3. Fix the photoresist-coated silicon oxide substrate onto the mask using PET tape, then place it on a heating platform at a constant temperature of 110 ℃ for 90 s.
  4. Place the photomask flat on the lithography area of the lithography machine, and perform photolithography patterning under the following lithography conditions: light voltage 0.65 V, time 6.5 s.
  5. Place the silicon oxide substrate with completed photolithography patterning in AZ-400K developer solution (stock solution: water = 1:4) for 60 s of development. After removal, clean thoroughly with deionized water, then dry using nitrogen gas.
  6. Sputter a 20 nm Ti layer and a 100 nm Au layer sequentially on the surface of the silicon oxide substrate using a magnetron sputtering instrument (power 50 W, time 600 s).
  7. Soak the substrate in acetone for 10 min, then wash off the excess photoresist.
  8. Rinse the prepared microelectrode chips with deionized water for 1 min, then dry with nitrogen for 1 min.
  9. Design the channel geometry width-to-length ratio 15:1 and a short channel of 4μm in the photomask
  10. Pattern PET tape (1.2 mm in length, 0.6 mm in width) using an ultraviolet laser cut-out machine as a window to align the position of the gate electrode.
  11. Sputter a 100 nm Pt layer sequentially on the surface of the gate electrode using a magnetron sputtering instrument (power 50 W, time 500 s).
  12. Pattern PET tape (60 μm in length, 15 μm in width) using an ultraviolet laser cut-out machine as a window to align the position of the channel.
  13. Spin-coat the channel following Steps 1.1.1 and 1.1.2.

3. Sensing performance of the OECT-based H2O2 sensor with the stacked PEDOT: BTB/PEDOT: PSS semiconductor layer

NOTE: When measuring the OECT-based H2O2 sensor under a fixed gate voltage of +0.6 V, do Step 3.1. When measuring under a fixed gate voltage of -0.6 V, follow Step 3.2.

  1. Measure the output current (IDS) variations with different H2O2 concentrations under a fixed gate voltage of +0.6 V.
    1. Dip 20 μL H2O2 solutions with different concentrations (configured in 0.1× PBS, ranging from 10-3 M to 10-11 M at intervals of two orders of magnitude) with the same conductivity of 34.39 ± 0.73 mS cm-1 sequentially on the channel surface.
    2. Connect the source, drain, and gate electrodes of the H2O2 sensor to a dual-port Source Meter, respectively.
    3. Apply VDS of -0.6 V, VG of +0.6 V, a measure time of 40-150 s to acquire the quasi-relative equilibrium output IDS, and a measurement duration of 10 s in single-stage constant voltage mode.
    4. Rinse the channel surface with deionized water prior to measuring the next H2O2 solution.
    5. Acquire the steady-state IDS value.
  2. Measure the IDS variations with different H2O2 concentrations under a fixed gate voltage of -0.6 V.
    1. Dip 20 μL of H2O2 solutions with different concentrations (configured in 0.1× PBS, ranging from 10-3 M to 10-11 M at intervals of two orders of magnitude) with the same conductivity of 34.39 ± 0.73 mS cm-1 sequentially on the channel surface.
    2. Connect the source, drain, and gate electrodes of the H2O2 sensor to the dual-port Source Meter, respectively.
    3. Apply VDS of -0.6 V, VG of -0.6 V, a measure time of 40-150 s to acquire the quasi-relative equilibrium output IDS, and a measurement duration of 10 s in single-stage constant voltage mode.
    4. Rinse the channel surface with deionized water prior to measuring the next H2O2 solution.
    5. Acquire the steady-state IDS value.

Results

This paper initially characterizes the stacked-layer PEDOT: BTB/PEDOT: PSS channel material using SEM, AFM, UV-vis spectroscopy, and electrochemical measurement. SEM and AFM images (Figure 1 and Figure 2) reveal that the 241 nm-thick stacked-layer PEDOT: BTB/PEDOT: PSS exhibits abundant granular structures, in contrast to the relatively smooth surface of the 120 nm-thick single-layer PEDOT: PSS film. The root-mean-square roughness (Rq) values are 3.02 nm for the single-layer film and 22.1 nm for the stacked-layer film, showing a significant difference and confirming successful electrodeposition of the stacked-layer film onto the Au substrate.

Investigations of the electrochemical and photoelectrochemical properties at the electrolyte/channel layer interface demonstrate that a fixed gate voltage of -0.6 V represents the optimal operating point for the stacked-layer PEDOT: BTB/PEDOT: PSS channel (Figures 3 and Figure 4). Additionally, the corresponding OECT-based H2O2 sensors are characterized under different fixed gate voltages and with different channel layers. Results clearly show that the stacked-layer PEDOT: BTB/PEDOT: PSS device at VG= -0.6 V (Figures 5C,D) exhibits a superior linear detection range (10-11–10-3 M) and an ultra-low LOD (1.8 × 10-12 M) compared with the same stacked-layer device at VG= +0.6 V (Figures 5A,B). Finally, standardized micro-nano fabrication procedures for OECT devices are described in detail to facilitate device reproduction for researchers in related fields (Figure 6).

Regarding the photoelectrochemical characteristics of the stacked layer, relevant tests are performed using UV–vis spectroscopy. Initially, obvious variations in the absorption spectra of the stacked-layer PEDOT: BTB/PEDOT: PSS are observed under different pH values rather than different H2O2 concentrations, indicating that an electrochemical reaction occurs between PEDOT: BTB and hydrogen ions rather than with H2O2 directly (Figure 3A,B). When the ITO electrode modified with the stacked-layer PEDOT: BTB/PEDOT: PSS is biased at +0.6 V or -0.6 V, the UV-vis absorption spectra remain nearly identical at different H2O2 concentrations, illustrating that no significant electrochemical reaction occurs in the absence of Pt as an electrocatalyst. Subsequently, a two-electrode electrochemical system is constructed using Pt and an ITO electrode modified with the stacked-layer PEDOT: BTB/PEDOT: PSS, in which absorption spectra vary with H2O2 concentrations. Notably, the absorption spectrum of Pt biased at -0.6 V (Figure 3C,D) shows a better linear relationship with changes in H2O2 concentration than those biased at +0.6 V (Figure 3E,F), highlighting the importance of voltage boundary conditions for H2O2 sensing. Determination of the VG operating point for the H2O2 sensor is achieved via electrochemical measurements. The VE is first measured in 0.1× PBS without H2O2, giving VE = -0.15 V at VG = +0.6 V and VE = -0.31 V at VG = -0.6 V (Figures 4A,C). Since the Ag/AgCl reference electrode and the source electrode are electrically shorted, the potential difference between VE and VG is +0.75 V for VG = +0.6 V and -0.29 V for VG = -0.6 V. The potential difference can be regarded as the effective working potential of the Pt electrode. Furthermore, CV measurements of Pt-catalyzed H2O2 oxidation/reduction are conducted in a three-electrode electrochemical system, revealing that the Pt electrode exhibits higher catalytic efficiency at a working potential of -0.29 V than at +0.75 V (Figure 4B,D). Accordingly, -0.6 V is determined as the optimal VG operating point for the H2O2 sensor.

We further compare the sensing performance of the H2O2 sensor at gate biases of -0.6 V and +0.6 V. Specifically, electrocatalytic reaction of H2O2 at Pt generates one Nernst potential Nernst equation formula, ENernst,H2O2, chemical potential in electrochemistry study., and the by-product hydrogen ions can further interact with BTB molecules in the PEDOT: BTB layer to produce a second Nernst potential Static equilibrium, equation \(E_{\text{Nernst,H}^+}\), chemistry calculation, formula., resulting in a synergistic signal amplification effect. At a gate bias of -0.6 V, increases in both Static equilibrium, equation \(E_{\text{Nernst,H}^+}\), chemistry calculation, formula. and Nernst equation formula, ENernst,H2O2, chemical potential in electrochemistry study. with rising H2O2 concentration lead to an increasing |IDS| and an ultra-low LOD (Figure 4E and Figure 5D). At a gate bias of +0.6 V, the decrease in Static equilibrium, equation \(E_{\text{Nernst,H}^+}\), chemistry calculation, formula. during H2O2 sensing results in a decreasing |IDS| and a correspondingly higher LOD (Figure 4Fand Figure 5B).

Scanning electron microscopy (SEM) of PEDOT:BTB/PEDOT:PSS film thickness and nanoparticle morphology.
Figure 1. Morphology characterizations of single PEDOT:PSS layer and stacked PEDOT: BTB/PEDOT:PSS layer. (A) Top-view SEM image of stacked-layer PEDOT:BTB/PEDOT:PSS (1 μm scale) with a zoomed inset (500 nm scale). (B) Top-view SEM image of single-layer PEDOT: PSS (500 nm scale). (C) Cross-sectional SEM image showing the thickness of stacked-layer PEDOT:BTB/PEDOT:PSS (241 nm PEDOT:BTB + 120 nm PEDOT:PSS). (D) Cross-sectional SEM image showing the thickness (115 nm PEDOT:PSS + 151 nm Au). This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

Surface morphology in AFM images: PEDOT:BTB/PEDOT:PSS vs PEDOT:PSS, height sensor analysis.
Figure 2. AFM characterizations in tapping mode. (A) Top-view and cross-sectional AFM images of the stacked-layer PEDOT:BTB/PEDOT:PSS film. (B) Top-view and cross-sectional AFM images of the single-layer PEDOT:PSS film. This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

<p>Electrochemical cell setup, optical spectroscopy, absorbance vs. wavelength graph, pH effect, H<sub>2</sub>O<sub>2</sub> concentration.</p>
Figure 3. UV-vis characterizations. (A) Schematic of the UV-vis setup for investigating the response of stacked PEDOT:BTB/PEDOT:PSS to solutions at different pH values. (B) Absorption spectra of stacked PEDOT:BTB/PEDOT:PSS at pH 3, 5, 7, and 9. (C) Schematic of the UV-vis setup for characterizing the H2O2 response of stacked PEDOT:BTB/PEDOT:PSS at a Pt gate bias of -0.6 V. (D) Absorption spectra of stacked PEDOT:BTB/PEDOT:PSS at various H2O2 concentrations from 10-3 to 10-11 M. (E) Schematic of the UV-vis setup for characterizing the H2O2 response of stacked PEDOT:BTB/PEDOT: PSS at a Pt gate bias of +0.6 V. (F) Absorption spectra of stacked PEDOT:BTB/PEDOT:PSS at various H2O2 concentrations from 10-3 to 10-11 M. This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

Electrochemical sensor setup, PEDOT:PSS electrode diagram, voltage-current graphs, H2O2 detection results.
Figure 4. Electrochemical characterization of optimal operating conditions for the H2O2 sensor. (A) Schematic of VE measurements based on the OECT device. (B) Schematic of CV measurements based on the three-electrode system. (C) VE measured in 0.1× PBS without H2O2 using a dual-port source meter and an oscillograph. (D) CV curves at different H2O2 concentrations catalyzed by the Pt electrode in a three-electrode system. (E) VE obtained in 0.1× PBS with various H2O2 concentrations at a VG of -0.6 V. (F) VE obtained in 0.1× PBS with various H2O2 concentrations at a VG of +0.6 V. This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

Electrochemical sensor diagram; PEDOT:BTB reactivity; Pt electrode; current vs. time graph.
Figure 5. H2O2 sensing based on the synergistic Nernst potential effect at gate biases of +0.6 V and -0.6 V. (A,C) Schematic illustrations of the sensing mechanism for the OECT device at VG of +0.6 V and -0.6 V. (B,D) Sensing performance of the OECT sensor with the stacked PEDOT:BTB/PEDOT:PSS at VG of +0.6 V and -0.6 V. This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

Photolithography process diagram: spin-coating, patterning, PEDOT:PSS deposition, barrier layers.
Figure 6. Fabrication process of the H2O2 sensor. (A) Lift-off of source/drain microelectrodes and Pt gate electrode. (B) Photoresist spin-coating and patterning. (C) Spin-coating PEDOT:PSS. (D) Deposition of PEDOT:BTB. (E) Photoresist removal. (F) Preparation of barrier layers. This figure is reproduced from Wang et al.13. Please click here to view a larger version of this figure.

MethodGate electrodeSemiconducting layerLinear rangeLODSensitivityResponse timeRef.
OECTPtPEDOT: PSS5 ×10-6~10-3 M5 μM//Cicoira et al.10
OECTPt NPs/MWCNTs/CPEPEDOT: PSS5×10-7~10-4 M2.0×10-7 M0.234 decade-1500 sGuo et al.11
ElectrochemistryRGO-Pt/GCE/5×10-7 ~3.475×10-3 M2×10-7 M459 ± 3 mA·M−1·cm−2/Zhang et al.15
ElectrochemistryCo3N NW/TM/2×10-6~2.8×10-2 M10-6 M139.9 μA·mM-1·cm-2/Xie et al.16
ElectrochemistryPt-ZnO/GCE/2×10-5~5×10-3 M1.5×10-6 M-3.94 μA·mM-1/Ke et al.17
ElectrochemistryPtPb/G/2×10-9~2.5×10-3 M2×10-9 M4.05 mA·mM-1·cm-2/Sun et al.18
ElectrochemistryAuNPs/Co-LDH/4×10-6~1.6×10-2 M1.9×10-7 M406.61 μA·mM-1·cm-2/Yuan et al.19
OECTCNT/Pt NPsPEDOT: PSS10-8~8×10-7 M/6.31×10-7 A·dec-1/Wu et al.20
OECTPt-CeO2 NS-MWCNTPEDOT: PSS10-7~10-4 M8.28×10-8 M0.118 decade-1/Liu et al.21
OECTPtPEDOT: PSS10-11~10-3 M1.8×10-12 M-1.18×10-4 A·dec-146.60 sThis work

Table 1: Performance comparison of the proposed OECT-based H₂O₂ sensor with representative electrochemical and OECT sensors reported in the literature. This table is reproduced from Wang et al.13.

Supplementary File 1: Theoretical analysis of the OECT-based synergistic Nernst potential mechanism. Please click here to download this file.

Discussion

The success of the protocol relies on three interdependent critical steps, each validated by experimental characterization. Firstly, the fabrication of the stacked-layer channel material (Protocol 1.1) requires precise control over PEDOT: PSS spin-coating (4200 rpm for 60 s, followed by baking at 130 °C) and PEDOT: BTB electrodeposition (where the short-circuited PEDOT: PSS channel serves as the working electrode, with an electric potential ranging from 0 to 1 V at a scan rate of 0.1 V s⁻1 for 15 cycles). Notably, dimension deviations (±10 nm) in the granular size and layer thickness exert a distinct impact on the interaction between BTB and H⁺ molecules, as illustrated by SEM/AFM characterization (Protocol 1.2.1, Figure 1 and Figure 2). Thus, the electrodeposited upper-layer PEDOT: BTB (241 nm) should uniformly overlay on the PEDOT: PSS channel material (120 nm) to ensure the generation of a reproducible synergistic Nernst potential (Supplementary File 1).

Subsequently, microelectrode fabrication (Protocol 2, Figure 6) is designed with a short channel length of 4 μm and a width/length ratio of 15:1 to compensate for the ion-transport hindrance of PEDOT: BTB, ensuring a measurable IDS despite reduced transconductance (6.58 mS for the stacked-layer channel device compared to 14.08 mS for the single-layer channel device). Finally, gate bias optimization at VG = -0.6 V (Figure 4E) is crucial for maximizing the synergistic Nernst potential effect, as corroborated by CV measurements (a redox potential of approximately -0.29 V with negligible variation across different H2O2 concentrations) (Figure 4D) and VE measurements (an VE of about -0.31 V) (Figure 4B,D). In contrast, a gate bias of VG = +0.6 V weakens the synergistic Nernst potential effect, deteriorating the LOD by over six orders of magnitude (Figure 4E,F and Figure 5B,D). Notably, the PEDOT: PSS thin film-modified Au rod is selected as the counter electrode primarily due to its inertness toward H2O2.

The critical step in the protocol is maximizing the homogeneity of the upper PEDOT: BTB layer electrodeposited on the single-layer PEDOT: PSS channel material. During the CV electrodeposition process, PEDOT: BTB is susceptible to non-uniform redox current sites within a given electrochemical potential range, resulting in distinct electrochemical current responses when interacting with H+ (a by-product of H2O2 catalysis). To address this issue in future work, we will adopt a spin-coating technique for PEDOT: BTB layer fabrication and select homogeneous OECT devices for pH response, aiming to achieve robust H2O2 biosensing.

This protocol outperforms other reported H2O2 sensors by leveraging synergistic Nernst potentials (Figure 5C,D), achieving an ultra-low LOD of 1.8 × 10-12 M. Additionally, H2O2 sensors fabricated using this protocol (Figure 6) can not only detect H2O2 residues in milk to assess potential adverse effects on human health22,23, but also be extended to the detection of analytes based on enzyme-catalyzed reactions. Finally, a comparison of the proposed H2O2 sensor with state-of-the-art sensors is presented in Table 1.

Disclosures

The authors have no conflicts of interest to disclose.

Acknowledgements

This research was supported by the National Natural Science Foundation of China (52175542 and 52203316), Science and Technology Cooperation and Exchange Special Project of Shanxi Province (No. 202304041101032), Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province (20240007), Research Project Supported by Shanxi Scholarship Council of China (No. 2024062), Patent Transformation Special Program of Shanxi Province (No. 202304012), China Postdoctoral Science Foundation (No. 2024M762331) Natural Science Foundation of Shanxi Province (No. 20210302123136 and 202103021223068), and the Shanxi Province doctoral innovation station (Xinzhou) for supporting this research.

Materials

List of materials used in this article
NameCompanyCatalog NumberComments
10× Phosphate Buffered Saline (PBS)Lanbolide Trading Co., LTDP7209Purity: ≥99%
3,4-ethylenedioxythiophene (EDOT)Shanghai Aladdin Biochemical Technology Co., Ltd., ChinaE105649-25gPurity: ≥99%
3-glycidoxypropyltrimethoxysilane (GOPS)Shanghai Aladdin Biochemical Technology Co., Ltd., ChinaG107576Purity: ≥97%
DeveloperSuzhou Yancai Weina Technology Co., Ltd.AZ 400K
Bromothymol Blue (BTB)Sinopharm Group Chemical Reagent Co., LTDB801811-25gPurity: ≥95%
Deionized waterShanghai Aladdin Biochemical Technology Co., Ltd., ChinaW11942418.2 Mfigure-materials-1 cm 
Digital microscopeOlympus Corporation of JapanDSX1000A cursory observation of the as-prepared OECT's channel
Dodecyl benzene sulfonic acid (DBSA)Shanghai Aladdin Biochemical Technology Co., Ltd., ChinaD106550Purity: ≥90%
Dual potentiostatic electrochemical workstationMetrohm AG, SwitzerlandVIONIC
Dual-port SourceMeterTek Technology Co., LTDKeithley 2636B
Dual-target magnetron sputteringShenyang Kejing Automation Equipment Co., LTDVTC-600-2HD
Ethylene glycol (EG)Shanghai Aladdin Biochemical Technology Co., Ltd., ChinaE119700Purity: ≥99.8%
Hydrogen peroxide (H2O2)Huize Biochemical CompanyELPurity: ≥35%
N-methyl1-2-pyrrolidone (NMP)Sigma-Aldrich (Shanghai) Trading Co., Ltd.328634Purity: ≥99.5%
Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS)Sigma-Aldrich (Shanghai) Trading Co., Ltd.739332Purity: ≥99.7%
Polyethylene terephthalate (PET)Sigma-Aldrich (Shanghai) Trading Co., Ltd.GF09063581
Potassium nitrate (KNO3)Sinopharm Group Chemical Reagent Co., LTD10017218Purity: ≥99.0%
PhotoresistSuzhou Yancai Micro-Nano Technology Co., LTDROL-7133
Scanning Electron Microscope (SEM)Carl Zeiss Company of GermanyGemini Sigma 300
Spin coaterJiangsu Leibo Scientific Instrument Co., LTDEZ4
Sulfuric acid (H2SO4)Sinopharm Group Chemical Reagent Co., LTD1002160895.0-98.0%
Atomic Force Microscopy (AFM)Bruker Corporation of the United StatesBruker Dimension Icon
Ultraviolet laser marking machineShanghai Cifang Electrical Technology Co., LTDRD-JW355
Ultraviolet-visible spectrophotometric spectroscopy (UV-vis)Ocean Insight Company of the United StatesOCEAN-HDX-UV-VIS

References

  1. Chen, W., Cai, S., Ren, Q. Q., Wen, W., Zhao, Y. D. Recent advances in electrochemical sensing for hydrogen peroxide: A review. Analyst. 137 (1), 49-58 (2012).
  2. Zeng, Z. Y., et al. A bioinspired flexible sensor for electrochemical probing of dynamic redox disequilibrium in cancer cells. Adv. Sci. 10 (36), (2023).
  3. Riaz, M. A., Chen, Y. Electrodes and electrocatalysts for electrochemical hydrogen peroxide sensors: A review of design strategies. Nanoscale Horiz. 7 (5), 463-479 (2022).
  4. Pratsinis, A., et al. Enzyme-mimetic antioxidant luminescent nanoparticles for highly sensitive hydrogen peroxide biosensing. ACS Nano. 11 (12), 12210-12218 (2017).
  5. Yan, Y., et al. Metal-organic framework-based biosensor for detecting hydrogen peroxide in plants through color-to-thermal signal conversion. ACS Nano. , (2022).
  6. Liu, R. X., et al. Colorimetric two-dimensional photonic crystal biosensors for label-free detection of hydrogen peroxide. Sens. Actuators B. 354, (2022).
  7. Rivnay, J., et al. Organic electrochemical transistors. Nat. Rev. Mater. 3 (2), (2018).
  8. Liu, J., et al. Organic electrochemical transistor-based immuno-sensor using platinum loaded CeO2 nanosphere-carbon nanotube and zeolitic imidazolate framework-enzyme-metal polyphenol network. Biosens. Bioelectron. 230, (2023).
  9. Fu, Y., et al. Highly sensitive detection of protein biomarkers with organic electrochemical transistors. Adv. Mater. 29 (41), (2017).
  10. Cicoira, F., et al. Influence of device geometry on sensor characteristics of planar organic electrochemical transistors. Adv. Mater. 22 (9), 1012(2010).
  11. Guo, X., et al. Organic electrochemical transistor for in situ detection of H2O2 released from adherent cells and its application in evaluating the in vitro cytotoxicity of nanomaterial. Anal. Chem. 92 (1), 908-915 (2020).
  12. Qi, G. Y., et al. High-performance, single-component ambipolar organic electrochemical transistors with balanced N/P-type properties for inverter and biosensor applications. Adv. Funct. Mater. 35 (2), (2025).
  13. Wang, Z. Q., et al. Ultra-low LOD H2O2 sensor based on synergistic Nernst potential effect. Adv. Sci. 12 (26), (2025).
  14. Shen, H., et al. A wearable electrowetting on dielectrics sensor for real-time human sweat monitor by triboelectric field regulation. Adv. Funct. Mater. 32 (34), (2022).
  15. Zhang, Y. Y., et al. Highly sensitive graphene-Pt nanocomposites amperometric biosensor and its application in living cell H2O2 detection. Anal. Chem. 86 (19), 9459-9465 (2014).
  16. Xie, F. Y., Cao, X. Q., Qu, F. L., Asiri, A. M., Sun, X. P. Cobalt nitride nanowire array as an efficient electrochemical sensor for glucose and H2O2 detection. Sens. Actuators B. 255, 1254-1261 (2018).
  17. Ke, X. L., et al. Fabrication of Pt-ZnO composite nanotube modified electrodes for the detection of H2O2. J. Electroanal. Chem. 817, 176-183 (2018).
  18. Sun, Y. J., et al. Graphene/intermetallic PtPb nanoplates composites for boosting electrochemical detection of H2O2 released from cells. Anal. Chem. 89 (6), 3761-3767 (2017).
  19. Yuan, J., et al. Cobalt-based layered double hydroxide nanosheet-supported AuNPs for high performance electrochemical H2O2 detection. Appl. Surf. Sci. 630, (2023).
  20. Wu, X. Y., et al. Fiber-shaped organic electrochemical transistors for biochemical detections with high sensitivity and stability. Sci. China Chem. 63 (9), 1281-1288 (2020).
  21. Liu, J. W., et al. Organic electrochemical transistor-based immuno-sensor using platinum loaded CeO2 nanosphere-carbon nanotube and zeolitic imidazolate framework-enzyme-metal polyphenol network. Biosens. Bioelectron. 230, (2023).
  22. Balu, S., Palanisamy, S., Velusamy, V., Yang, T. C. K. Sonochemical synthesis of gum guar biopolymer stabilized copper oxide on exfoliated graphite: Application for enhanced electrochemical detection of H2O2 in milk and pharmaceutical samples. Ultrason. Sonochem. 56, 254-263 (2019).
  23. Abbas, M. E., Luo, W., Zhu, L. H., Zou, J., Tang, H. Q. Fluorometric determination of hydrogen peroxide in milk by using a fenton reaction system. Food Chem. 120 (1), 327-331 (2010).

Reprints and Permissions

Tags

Pt Gate ElectrodeBromothymol BluePEDOT PSSUV Vis SpectroscopyElectrochemical MeasurementsSpin CoatingMagnetron Sputtering
Contact Us
Recommend to Library

Privacy

Terms of Use

Policies

Copyright © 2026 MyJoVE Corporation. All rights reserved.